Oscillating platen for abrading tool



g- 22, 1 67 s. G. ENDERS 3,336,702

OSCILLATING PLATEN FOR ABRADING TOOL Filed Feb. 28, 1 964 2 Sheets-Sheet 1.

, A INVENTOR SHERWOOD G. ENDERS ATTORNEY Aug. 22, 1967 s. e. ENDERS 3,336,702

QSCILLATING PLATEN FOR ABRADING TOOL Filed Feb. 28, 1964 2 SheetsShe'et 2 FIG. 9 38b FIG. 6

. INVENTOR SHERWOOD e. ENDERS BY I ATTORNEY United States Patent 3,336,702 OSCILLATING PLATEN FOR ABRADING TOOL Sherwood G. Enders, Bowleys Quarters, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Filed Feb. 28, 1964, Ser. No. 348,124 13 Claims. (Cl. 51-170) The present invention relates to a means for resiliently mounting an oscillating platen to the housing of an abrading tool, and more particularly, to an improved resilient mounting means for the oscillating platen of a portable electric sander, one whose housing preferably comprises a pair of complementary mating halves detachably secured together along a common longitudinal midplane.

It is an object of the present invention to provide an improved platen retaining means for a portable electric sander (or similar tool) having a split housing, one which is usually referred to in the art as a clam shell design.

It is another object of the present invention to facilitate the economical fabrication and assembly of an abrading tool having an oscillating platen.

It is yet another object of the present invention to provide a low-cost platen subassembly which may be assembled to the abrading tool quickly and conveniently.

It is a further object of the present invention to provide an improved platen retaining means, one which is rugged and reliable for extended usage.

It is a still further object of the present invention to provide a platen retaining means which utilizes a plurality of resilient posts, each of which is homogeneously molded of a suitable rubber composition and is entirely free of any molded-in inserts of the type habitually restorted to in the prior art.

In accordance with the broad teachings of the present invention, there is herein illustrated and described, an abrading tool having an oscillating platen, a housing comprising a pair of housing portions secured together, and an imporved means for resiliently mounting the platen to the housing. This improved resilient mounting means comprises at least one pair of spaced-apart resilient members, preferably in .the form of resilient posts, each of which comprises an upper portion, a main body portion, and a lower portion seated on the platen. Means are provided to trap the respective lower portions of the resilient posts against the platen. A spacer means is positioned between the respective upper portions of the posts, and means are provided to independently trap the respective upper portions of the posts between the spacer means and the housing portions as the housing portions are secured together.

In accordance with the further teachings of the present invention, there is herein illustrated and described, a preferred embodiment of an abrading tool, such as a portable electric sander of the orbital type, comprising an oscillating platen, a split housing including a pair of complementary mating halves detachably secured together along a common longitudinal midplane, and an improved means for resiliently mounting the platen to the housing. This improved resilient mounting means comprises two pairs of resilient posts positioned front and back on the platen, respectively, with each pair of resilient posts comprising a first post and a second post spaced from one another on opposite sides of the common longitudinal midplane. The resilient posts are substantially identical to one another; and each comprises an upper portion having an external annular groove formed therein, a substantially cylindrical main body portion, and a lower portion having a flanged collar or foot resting on the platen and positioned thereon. A bracket is seated on top of the respective flanged collars of the posts; and

means are provided to secure each bracket to the platen, preferably at a point intermediate the posts, thereby trapping the respective flanged collars of the posts against the platen. A spacer member is positioned between the respective upper portions of each pair of posts, and means are provided to independently trap the respective upper portions of the posts between the spacer member and the mating halves of the split housing as the mating halves are secured together.

In accordance with the still further teachings of the present invention, a platen subassembly is provided, comprising a substantially planar resilient pad and a rigid backing member bonded on top of the pad. Four upstanding resilient posts are arranged in dual pairs front and back, respectively, on top of the backing member. A raised boss is formed on the backing member intermediate each pair of posts. A pair of spaced-apart lanced-out raised tabs are formed on the backing member to each side of the raised boss. Each resilient post has a lower flanged collar or foot which is positioned between a portion of a respective boss and a respective pair of raised tabs. One of the raised tabs projects above a respective flanged collar, and the other tab is below the respective collar. A pair of brackets are provided, one for each pair of posts. Each bracket has a pair of circular openings by means of which the bracket is fitted over a respective pair of posts and is seated on the respective flanged collars of the posts. Each bracket further has a slotted opening formed therein radially of each circular opening, and the projecting tabs are received in the respective slotted openings, thereby positioning each bracket with respect to the backing member. Each boss has an opening formed therein to communicate with an opening formed in the resilient pad; and a screw or other suit-able fastening member passes through the communicating openings to secure each bracket to the backing member, thereby trapping the respective lower flanged collars of the posts against the backing member. Preferably, an external annular relief is formed in each post directly above its flanged collar, thereby preventing any chafing of the post against a re spective circular opening in the bracket.

These and other objects of the present invention will become apparent from a reading of the following specification, taken in conjunction with the enclosed drawings, in which:

FIGURE 1 is a perspective view of a typical abrading tool with which the teachings of the present invention may find particular utility, the tool preferably having a split housing comprising a pair of complementary mating halves detachably secured together along a common longitudinal midplane;

FIGURE 2 is a fragmentary side elevation, taken along the lines 2-2 of FIGURE 1, enlarged over the scale of FIGURE 1, with part of the housing being broken away to illustrate (in elevation) two of the four resilient posts which mount the oscillating platen to the housing, the illustrated posts both being on the same side of the common .longitudinal midplane;

FIGURE 3 is a vertical section taken along the lines 33 of FIGURE 2, enlarged slightly over the scale of FIGURE 2, and showing the manner in which the respective lower flanged collar portions of a pair of resilient posts (on opposite sides of the common longitudinal midplane from each other) are trapped against the platen by means of a bracket secured to the platen, while the respective upper portions of the pair of posts are trapped between a rigid spacer member and the mating halves of the split housing as the mating halvesare secured together;

FIGURE 4 is a transverse section view taken along the lines 44 of FIGURE 3;

Patented Aug. 22, 1967 j FIGURE 5 is a top plan view of the oscillating platen (to a slightly reduced scale), the broken lines showing the respective lower flanged collars of the resilient posts positioned on top of the platen;

FIGURE 6 is a fragmentary exploded view showing a pair of resilient posts, a portion of the platen to which the posts are to be secured, a bracket member fitting over the posts and adapted to be seated upon the respective flanged collars of the posts, and a screw passing up through a boss in the platen to secure the bracket to the platen, thereby trapping the posts against the platen;

FIGURE 7 is a fragmenary perspective view of a portion of the platen, showing the positioning of the respective flanged collars of a pair of resilient posts between a raised boss and a respective pair of lanced-out raised tabs formed on the platen to each side of the boss;

FIGURE 8 is a fragmentary perspective view of a portion of the platen, showing the pair of resilient posts, the bracket secured to the platen to trap the posts against the platen, the rigid spacer member disposed between respective upper portions of the resilient posts, and the paper clamp member retained by the outwardly-extending semi-cylindrical portion of the bracket, the broken lines illustrating the blade of a screwdriver engaged in a slot in the paper clamp member to turn the clamp member in one direction or the other, thereby clamping or unclamping the abrasive paper to the platen;

FIGURE 9 is a fragmentary exploded view showing the manner in which the platen subassembly is trapped between the mating halves of the split housing of the tool, the view showing (from top to bottom) a rear portion of the top mating half of the split housing; the rear portion of the platen subassembly having a respective pair of resilient posts, the lower portions of which are trapped by the bracket against the top surface of the platen, and the upper portions of which have the rigid spacer member positioned therebetween; and the rear portion of the bottom mating half of the split housing, showing in greater detail one of the internal bosses formed in the mating housing half, the accessible opening in the boss, the slotted recess formed across the opening and communicating therewith, and the semi-annular tongue in the bottom of the slotted recess, the tongue being received in a circumferential portion of the external annular groove formed in the respective. resilient post.

With reference to FIGURE 1, there is illustrated a portable electric orbital sander 10 with which the teachings of the present invention may find particular utility; however, it will be appreciated by those skilled in the art that the teachings of the present invention are equally applicable to a wide variety of power-driven abradingtype of tools. With this in mind, the sander 10 is preferably of the familiar clam shell housing design and comprises a split housing having a pair of complemetnary mating halves 11 and 12 which are preferably die cast from a suitable material, such as aluminum, and are detachably secured together along a common longitudinal midplane, which is designated by the letter A. The mating half 12 of the split housing may be designated as the bottom half into which the components are assembled, while the mating half 11 may be designated as the top half or cover. The mating halves 11 and 12 of the split housing enclose a conventional electric motor and an eccentric driving mechanism, but these elements form no part of the present invention and hence are omitted for clarity of understanding. A rearward handle 13 is formed integrally with the mating halves of the split housing and includes an electric switch 14 by means of which the motor is energized from a suitable electric line L. A front handle or hand rest 15 is also formed integrally with the mating halves of the split housing for superior manual control of the tool. A plurality of air inlet slots 16 are formed in the housing to receive cooling air for the motor, and a plurality of air exit slots 17 are also formed in the housing for discharging the cooling air. An oscillating platen 18 (in the nature of a rubbing shoe) is driven by the eccentric driving mechanism in a manner understood by those skilled in the art, and the platen 18 is resiliently mounted to the housing in accordance with the teachings of the present invention.

With reference to the remaining drawings, the oscillating platen 18 may have any convenient configuration, but preferably, it is rectangular in plan outline, see FIG- URE 5, and comprises a planar resilient pad 19 which is bonded to a rigid support or backing member 20, both of which are shown in longitudinal section in FIGURE 3. The backing member 20 comprises a substantially-fiat oblong piece which is preferably stamped-out from a suitable sheet metal and is provided with bent-up side edges 21 and 22 as well as bent-up end edges 23 and 24. A raised boss 25, preferably of circular outline, is formed near each end of the platen, see FIGURE 5 again, and a pair of spaced-apart lanced-out raised tabs 26 and 27 are formed on the backing member to each side of a respective boss.

A plurality of resilient members comprising upstanding resilient posts 28 are provided; and as shown by the broken lines in FIGURE 5, there are four resilient posts arranged in dual pairs front and back, respectively, on the platen. Each pair of resilient posts 28, see FIGURE 3, comprises a first post and a second post spaced from each other on opposite sides of the common longitudinal midplane A. Each resilient post 28, see FIGURE 11 is entirely free of any integrally-molded inserts or other molded-in fastening members, and instead, is homogeneously molded throughout of a resilient material, such as a rubber composition; hence its manufacture is rendered convenient, simple, and economic. Each resilient post 28, see FIGURE 11 again, comprises an upper portion 29 having an external annular groove 30 formed therein, a substantially-cylindrical main body portion 31, and a lower portion provided with a flanged collar (or foot) 32. Each flanged collar 32, see FIGURE 7, is seated on the top surface of the platen between a circumferential portion of a respective boss 25 and a respective pair of lanced-out raised tabs 26 and 27, thereby providing the meansv by which the respective flanged collars 32 of the resilient posts 28 are positioned with respect to the platen. One of the raised tabs, 26, projects above the respective flanged collar 32, see FIGURE 7 again, while the other raised tab 27 is below the respective collar, the purpose of which will become apparent.

A bracket member 33 is provided, one for each pair of resilient posts. As shown more clearly in perspective view in FIGURE 6, the bracket 33 comprises a stampedout sheet metal piece having a pair of circular openings 34 by means of which the bracket is fitted over the pair of resilient posts 28 and is seated upon the respective flanged collars 32. The bracket 33 is further provided with a slotted opening 35 formed radially of each circular opening 34. The projecting raised tabs 26, see FIG- URE 8, are received in the respective slotted openings 35, thereby providing the means by which the brackets 33 are positioned with respect to the platen. Each bracket 33 is secured to the platen intermediate a respective pair of resilient posts; and the means for securing each bracket 33 comprises, see FIGURES 3 and 6, a screw 36 or suitable fastening member, communicating holes 37a and 37b formed in the pad 19 and backing member 20, respectively, to receive the screw, a lock washer 38a, and a lock nut 3811.

Each bracket 33 is thus secured to the oscillating platen 18 by a single fastening means which includes the respective screw 36 intermediate of the pair of resilient posts 28; and in the process of securing the respective bracket 33 to the platen 18, it will be appreciated that the respective lower flanged collars 32 of the resilient posts 28 are trapped against the top surface of the platen 18. It will be recalled that the resilient posts 28, see FIGURE 11 again, are entirely free of any molded-in inserts of the type which are habitually resorted to in the prior art; and in lieu of any inconvenient and expensive molded-in inserts, means are provided, including the respective brackets 33, to trap the respective lower portions of the posts 28 against the oscillating platen. This entrapment of the respective lower flanged collars 32 of the posts 28 causes the resilient material to be compressed vertically and to thereby flow radially (in a horizontal plane parallel to the platen) thereby facilitating the proper orbital motion that is imparted to the oscillating platen 18. Moreover, each resilient post, see FIGURES 3 and 11, is further provided with an external annular relief 39 between its main body portion 31 and its lower flanged collar 32. The purpose of this relief 39 is to prevent any undue rubbing or chafing between each resilient post 28 and the respective circular opening 34 formed in the bracket 33.

Each bracket 33 is further provided, see FIGURES 2 and 6, with an outwardly-extending substantially semicylindrical portion 40 which is concave with respect to the backing member 20, and a paper clamp member 41 has its cylindrical shank 41a retained between the backing member 20 and the concave portion 40 of the bracket 33. The paper clamp member 41, which by itself is wellknown in the art, has a plurality of axially-spaced knurled cylindrical sections 42 which are adapted to grip the disposable sandpaper 43 or other suitable abrading paper. As shown in broken lines in FIGURE 8, the blade of a screwdriver 44 may be inserted in a slot 45 formed in the end of the paper clamp member 41, and the paper clamp member 41 may be turned (in one direction or the other) in the journal created by the semi-cylindrical concave portion 40 of the bracket 33, thereby clamping (or unclamping) the sandpaper 43 from the platen 18.

After the four resilient posts 28 are secured to the platen 18 in the manner previously described, a rigid spacer member 46 is positioned between the respective upper portions of a pair of posts, see FIGURE 8; and then the entire platen subassembly, see FIGURE 9, is preferably turned ninety degrees so that the platen 18 is disposed in a vertical plane. Each spacer member 46, see FIGURE 10, comprises a rigid substantially-flat rectangular piece, which is preferably molded from a suitable plastic. A semi-circular cut-out 47 is formed in each end of the spacer member 46, and each cut-out 47 is received in a circumferential portion of a respective external annular groove 30 formed in the upper portions of the resilient posts 28. Preferably, an integral web formation 48 is provided on each side of the flat molded spacer member 46 for strengthening reasons.

As shown more clearly in FIGURE 9, each housing portion (comprising the mating halves 11 and 12 of the split housing) is provided with a pair of spaced inter- 'nal bosses 49 formed therein, one for each of the resilient posts 28. Each boss 49 has an opening 50 which faces towards (and is thus accessible from) the common longitudinal midplane A between the mating halves 11 and 12 of the split housing. A slotted recess 51 is formed across the opening 50 and communicates therewith, and each slotted recess 51 is disposed in a plane which is substantially parallel to the platen 18. A substantially semiannular tongue 52, see FIGURE 9, is integrally cast within the bottom of each slotted recess 51; and as shown more clearly in FIGURE 4, the tongue 52 is received within a circumferential portion of a respective external annular groove 30 in a resilient post 28, the portion of the groove whichis occupied by the tongue 52 being diametrically-opposite to that which is occupied by the spacer member 46. Each spacer member 46 is slidably guided or received in a respective one of the slotted recesses 51, and preferably, the end of the spacer 46, see FIGURE 4 again, has a clearance with respect to the extremities of the respective semi-annular tongue 52. ,7 When the mating halves 11 and 12 are secured together, the upper portion of each resilient post 28 will be trapped between one end of the spacer member 46 and a respective one of the cast-in tongues 53, see FIGURE 4, such that the 'pair of resilient posts 28 are trapped between the spacer member 46 and the mating halves 11 and 12 of the split housing as the mating halves are secured together; and this entrapment of the upper portions of the resilient posts 28 is entirely independent of the previouslydescribed entrapment of the lower flanged collar portions 32 against the platen 18.

The mating halves 11 and 12 of the split housing may be secured together in any convenient manner. Preferably, however, the mating halves are secured together by means of a plurality of screws 53, one of which is shown in FIGURE 9; the screws 53 are received in respective tapped recesses 54 located in respective bosses 55 formed in the bottom half 12 of the split housing.

The eccentric driving mechanism, designated broadly by the numeral 56 in FIGURE 2, forms no part of the present invention and hence has not been disclosed in detail. However, for a detailed description of a preferred embodiment of an eccentric driving mechanism, reference may be made to my co-pending application Ser. No. 332,148 filed on Dec. 20, 1963, entitled Driving Mechanism for Abrading Tool, assigned to the assignee of the present invention, and issued on Aug. 10, 1965, as Patent No. 3,199,251.

The advantages of the construction and teachings of the present invention may be reviewed and summarized briefly as follows: The bracket 33, one at each end of the platen 18, comprises a stamped sheet-metal piece which serves a dual function: one, to trap the lower flanged collars (or feet) 32 of the resilient posts 28 against the top surface of the platen 18; and two, to position and retain the paper clamp member 41 on the platen. Moreover, each bracket 33 is secured to the platen 18 by means of a single screw 36. The raised bosses 25 on the platen 18 assist in the positioning of the resilient posts 28 and allow the respective flanged collars 32 of the posts to be compressed, but not crushed. The resilient posts 28 are simple, economical molded pieces that are entirely free of any molded-in inserts. The whole platen subassembly is pre-assembled as a unit and is independently trapped between the mating halves 11 and 12 of the split housing as the mating halves are secured together. No additional fasteners are required to retain the platen subassembly to the housing, but rather, the very act of securing the mating housing halves together, which is necessary anyway, is used for the additional purpose of resiliently retaining the platen to the housing. The resulting structure achieves an economy of manufacture and a simplicity of design, yet one which is consonant with a rugged, reliable tool.

Not only may the teachings of the present invention be used in conjunction with any suitable eccentric driving mechanism, but moreover, the housing for the abrading tool need not be split longitudinally inasmuch as the teachings of the present invention contemplate an entrapment of the resilient posts between any suitable mating housing portions.

Obviously, manny modifications may be made without departing from the basic spirit of the present invention; and accordingly, within the scope of the appended claims, the invention may be practiced other than has been specifically described herein.

I claim:

1. In an abrading tool, having a housing, a platen subassembly comprising:

(a) a substantially-planar platen member below the housing;

(b) at least one 'pair of spaced-apart substantiallycylindrical resilient posts, each of said posts comprising:

(1) an upper portion retained on the housing;

(2) a main body portion; and

(3) a lower portion having a-fianged collar resting on the platen;

(c) a raised boss formed on the platen intermediate said posts;

((1) a pair of spaced-apart lanced-out raised tabs formed on the platen to each side of said boss;

(e) each of said flanged collars being positioned between a portion of said boss and a respective pair of raised tabs;

(f) at least one of said raised tabs projecting above a respective flanged collar;

(g) a bracket member having a pair of circular openings, whereby said bracket member is fitted over said posts and is seated on said boss and on top of said respective flanged collars of said posts;

(b) said bracket member further having a slotted opening radially of each circular opening to receive said respective raised tab; and

(i) fastening means projecting through said boss to secure said bracket member to the platen, whereby said respective flanged collars of said posts are trapped between said bracket member and the platen.

2. In an abrading tool, the combination of:

(a) a housing comprising a pair of mating housing portions detachably secured together along a common plane;

(b) an oscillating platen below the housing;

(c) at least one pair of spaced-apart resilient posts, one post on a respective side of the common plane, and each of said posts comprising:

(1) an upper portion having an external annular groove formed therein;

(2) a main body portion; and

(3) a lower portion secured to the planten;

(d) an internal boss formed in each of the housing portions, one for each post;

(e) said boss having an access opening facing in a direction away from the housing portion and towards the common plane;

(f) said boss further having a slotted recess formed across said opening and communicating therewith, said slotted recess being in a plane substantially parallel to the platen;

(g) a substantially semi-annular tongue in the bottom of said slotted recess, whereby said tongue is received in a first circumferential portion of the external annular groove in a respective one of said posts; and

(h) a substantially-planar rigid spacer member positioned between said upper portions of said posts, said spacer member transversely intersecting the common plane; and

(i) said spacer member having a cut-out portion at each end received in a second circumferential portion of said respective external annular groove which is opposite to said respective tongue, whereby said posts are trapped between said spacer member and the housing portions.

3. In an abrading tool, the combination of:

(a) a split housing comprising a pair of complementary mating halves secured together along a common longitudinal midplane;

(b) a substantially-planar oscillating platen below the housing;

(c) two pairs of resilient posts positioned front and back on the platen, each pair comprising:

( 1) a first post; and

(2) a second post spaced from said first post on the opposite side of the common longitudinal midplane;

(d) said first and second posts being substantially identical to one another and each comprising:

(1) an upper portion;

(2) a substantially-cylindrical main body portion;

and

(3) a lower portion having a flanged collar resting on the platen;

(e) means to position said respective flanged collars on the platen;

(f) a bracket member, one for each pair of posts;

(g) each bracket member being seated on top of said respective flanged collars and being secured to the platen intermediately of said posts, thereby trapping said respective flanged collars of said posts against the platen;

(h) a substantially-rigid spacer member disposed between the respective upper portions of each pair of posts substantially transverse to the midplane; and

(i) means to independently trap the respective upper portions of said posts between said spacer member and the mating halves of the split housing; said means including means to exert a transverse clamping pressure upon the upper portion of each post between a respective one of the mating halves of the split housing and a respective end of the spacer member.

4. The improvement of claim 3, wherein said means to position said respective flanged collars on the platen comprises:

(a) a raised boss formed on the platen intermediate each pair of posts; and

(b) a pair of spaced-apart lanced-out raised tabs formed on the platen to each side of each boss, whereby each flanged collar is seated between a portion of a respective boss and a respective pair of raised tabs.

5. The improvement of claim 3, wherein:

(a) said bracket member includes an outwardly-extending semi-cylindrical portion which is concave with respect to the platen; and wherein:

(b) a paper clamp member has a cylindrical shank portion journaled between the platen and said semicylindrical portion of said bracket member;

(c) said paper clamp member having a plurality of axially-spaced knurled cylindrical portions on each side of its shank portion to grip a disposable abrasive paper.

6. In an abrading tool, the combination of:

(a) a split housing comprising a pair of complementary mating halves secured together along a common longitudinal midplane;

(b) a substantially-planar oscillating platen below the housing;

(c) two pairs of resilient posts positioned front and back on the platen, each pair comprising:

(1) a first post; and

(2) a second post spaced from said first post on the opposite side of the common longitudinal midplane;

(d) said first and second posts being substantially identical to one another and each comprising:

(1) an upper portion having an external annular groove formed therein;

(2) a substantially-cylindrical main body portion;

and

(3) a lower portion having a flanged collar resting on the platen;

(e) a raised boss formed on the platen intermediate each pair of posts;

(f) a pair of spaced-apart lanced-out raised tabs formed on the platen to each side of each boss;

(g) said flanged collar of each post being positioned between a portion of a respective boss and a respective pair of raised tabs;

(h) at least one of said tabs projecting above a respective flanged collar;

(i) a bracket member for each pair of posts, each bracket member comprising:

(1) a substantially-flat piece having a pair of circular openings, one for each post whereby said bracket member is fitted over said posts; and

(2) a slotted opening formed in said bracket member radially of each circular opening to receive said one projecting tab, thereby positioning said bracket member with respect to the platen;

(j) means including a fastening member passing through said boss to secure said respective bracket member to the platen, whereby said flanged collars of said respective posts are trapped against the platen;

(k) a spacer member positioned between portions of the respective external annular grooves in said respective upper portions of each pair of posts; and

(1) means to trap the respective upper portions of each pair of posts between its respective spacer member and the' mating halves of the split housing.

7. The improvement of claim 6, wherein:

(a) the main body portion of each post has an external annular relief formed therein directly above its flanged collar, thereby preventing any chafing of said post against the respective circular opening in said bracket.

8. The improvement of claim 6, wherein said spacer member comprises: p

(a) a rigid substantially-flat rectangular molded piece having:

(1) a semi-circular cut-out in each end received in a circumferential portion of said respective external annular groove of each post; and further having:

(2) an integral strengthening web formation on each side of said flat piece.

9. The improvement of claim 6, wherein said means to trap the respective upper portions of each pair of posts between its respective spacer member and the mating halves of the split housing, comprises:

'(a) a pair of internal bosses formed in each of the housing halves, one boss for a respective one of said posts;

(b) said boss having an opening which faces towards the common longitudinal midplane between the mating halves;

(c) said boss further having a slotted recess formed across said opening and communicating therewith; (d) said slotted recess being in a plane substantially parallel to the platen;

(e) a substantially-semi-annular tongue in the bottom of said slotted recess, whereby said tongue is received in a first circumferential portion of a respective external annular groove in said respective post; and

(f) each end of said spacer member being slidably received in a respective one of said slotted recesses; and

(g) each end of said spacer member having a cut-out received in a second circumferential portion of said respective external annular groove which is opposite from said respective semi-annular tongue, thereby trapping the upper portion of each post between one end of said spacer member and a respective one of said tongues.

10. The improvement of claim- 9, wherein:

(a) a clearance is provided between the end of said spacer member and the extremities of said respective tongue.

11. In a portable power-driven tool, a platen subassembly, comprising:

(a) a substantially-planar resilient pad;

(b) a rigid backing member bonded on top of said pad;

(c) four upstanding resilient posts arranged in dual pairs front and back, respectively, on top of said backing member;

(d) a raised boss formed on said backing member intermediate each pair of posts;

(e) a pair of spaced-apart lanced-out raised tabs formed on said backing member to each side of said boss;

(f) each of said resilient posts having a lower flanged collar positioned between a portion of a respective boss and a respective pair of raised tabs;

10 (g) at least one of said raised tabs projecting above a respective flanged collar;

(h) a pair of brackets, one for each pair of posts;

(i) each bracket having a pair of circular openings, whereby each bracket is fitted over a respective pair of posts and is seated on said respective flanged collars;

(j) each bracket further having a slotted opening radially of each circular opening, whereby said projecting tabs are received in said slotted openings, respectively, to position each bracket with respect to said backing member;

(k) each boss having an opening formed therein to communicate with an opening formed in said resilient pad; and

(1) means including a fastening member passing through said communicating openings to secure each bracket to said backing member, thereby trapping the respective lower flanged collars of said posts against said backing member.

12. In a portable power-driven tool, a platen subassem-bly comprising:

(a) a substantially-planar resilient pad;

(b) a rigid backing member bonded on top of said pad;

(c) four upstanding resilient posts arranged in dual pairs front and back, respectively, on top of said backing member;

(d) each of said posts having a lower flanged collar resting on top of said backing member;

(e) means to position the respective flanged collars of said posts on said backing member;

(f) a pair of brackets, one for each pair of posts;

(g) each bracket being seated on said flanged collars of a respective pair of posts;

(h) means to position each bracket with respect to the platen;

(i) each bracket having an outwardly-extending semicylindrical portion which is concave with respect to said backing member;

(j) a pair of paper clamp members, one for each bracket;

(k) each paper clamp member having a cylindrical shank portion journaled between said backing member and the semi-cylindrical portion of a respective bracket;

(1) said paper clamp member further having a plurality of axially-spaced knurled cylindrical sections to grip a disposable abrasive paper; and

(m) means to secure each bracket to said backing member intermediate said respective pair of posts, thereby trapping the respective flanged collars of said posts between said respective brackets and said backing member, and thereby retaining said paper clamp member in its journal.

13. In an abrading tool, the combination of:

(a) a split housing comprising a pair of complementary mating halves fitted together along a common longitudinal midplane;

(b) means to secure the halves together; said means exerting a clamping pressure transverse to the common longitudinal midplane;

(c) an oscillating platen below the housing;

(d) four resilient posts disposed on the platen; said posts being arranged in two pairs, one pair at the front of the platen and the other pair at the rear of the platen, whereby an individual post of each pair is disposed on a respective side of the common longitudinal midplane;

(e) each of said posts having respective upper and lower portions;

(f) means to retain the lower portion of each post to the platen;

(g) a spacer member disposed between the respective upper portions of each pair of posts; each spacer transversely intersecting the common longitudinal midplane;

(h) each spacer having a pair of ends, and each end engaging a respective post on the side of the post which is nearest to the common longitudinal midplane; and

(i) a plurality of elements formed in the housing, one element for each post, and each element engaging its respective post on the side of the post which is furthest from the midplane; and

(j) each spacer having a transverse clearance with respect to the respective elements in the housing;

(k) whereby the transverse clamping pressure exerted by the means to secure the housing halves together is taken up by the resilient posts; and

(1) whereby the respective upper portions of each pair of posts are trapped between the complementary mating halves of the split housing.

References Cited UNITED STATES PATENTS Crosby 51170 Happe 51170 Atkin 51-170 Robins 51170 Amsden 5l170 Jepson 51170 Sheps 51170 X LESTER M. SWINGLE, Primary Examiner.

J. A. MATHEWS, Assistant Examiner. 

1. IN AN ABRADING TOOL, HAVING A HOUSING, A PLATEN SUBASSEMBLY COMPRISING: (A) A SUBSTANTIALLY-PLANAR PLATEN MEMBER BELOW THE HOUSING; (B) AT LEAST ONE PAIR OF SPACED-APART SUBSTANTIALLYCYLINDRICAL RESILIENT POSTS, EACH OF SAID POSTS COMPRISING: (1) AN UPPER PORTION RETAINED ON THE HOUSING; (2) A MAIN BODY PORTION; AND (3) A LOWER PORTION HAVING A FLANGED COLLAR RESTING ON THE PLATEN; (C) A RAISED BOSS FORMED ON THE PLATEN INTERMEDIATE SAID POSTS; (D) A PAIR OF SPACED-APART LANCED-OUT RAISED TABS FORMED ON THE PLATEN TO EACH SIDE OF SAID BOSS; (E) EACH OF SAID FLANGED COLLARS BEING POSITIONED BETWEEN A PORTION OF SAID BOSS AND A RESPECTIVE PAIR OF RAISED TABS; (F) AT LEAST ONE OF SAID RAISED TABS PROJECTING ABOVE A RESPECTIVE FLANGED COLLAR; (G) A BRACKET MEMBER HAVING A PAIR OF CIRCULAR OPENINGS, WHEREBY SAID BRACKET MEMBER IS FITTED OVER SAID POSTS AND IS SEATED ON SAID BOSS AND ON TOP OF SAID RESPECTIVE FLANGED COLLARS OF SAID POSTS; (H) SAID BRACKET MEMBER FURTHER HAVING A SLOTTED OPENING RADIALLY OF EACH CIRCULAR OPENING TO RECEIVE SAID RESPECTIVE RAISED TAB; AND (1) FASTENING MEANS PROJECTING THROUGH SAID BOSS TO SECURE SAID BRACKET MEMBER TO THE PLATEN, WHEREBY SAID RESPECTIVE FLANGED COLLARS OF SAID POSTS ARE TRAPPED BETWEEN SAID BRACKET MEMBER AND THE PLATEN. 